It is well known that layered materials, such as phyllosilicates, can be separated or exfoliated into their individual clay platelets, as disclosed in this assignee's U.S. Pat. Nos. 5,552,469; 5,578,672; and 5,698,624. The exfoliated platelets are useful as fillers for polymeric materials to achieve increases in strength, temperature resistance, gas impermeability, and other properties. While the technology has existed for many years for exfoliating clay platelets and combining such clay platelets with polymeric materials, this technology has not been commercialized, for one reason, among others, that while the addition of exfoliated clay platelets to the polymeric materials has substantially enhanced one or more properties of the polymer, the addition of clay impurities together with the exfoliated platelets has caused a marginal improvement, or has actually caused a decrease in properties that the platelets are designed to increase. Thus far, it has been impossible to sufficiently purify a layered material, such as a phyllosilicate, particularly a smectite clay, such that exfoliated platelets obtained from the purified clay are sufficiently free from clay impurities to significantly enhance the desired properties of the polymer.
The present invention includes a method for purifying such purifiable clays in order to manufacture polymer-grade, purified clay useful in nanocomposites.